Climate-Sensitive Building Renovation Strategies: A Review of Retrofit Interventions Across Climatic and Building Typologies

Abstract

Building renovation is widely recognised as a critical strategy for improving energy performance, reducing greenhouse gas emissions, and meeting decarbonisation targets. Although numerous studies have explored retrofit interventions, the existing literature tends to focus on either specific climates or particular building types, lacking a consolidated perspective that links interventions to both climatic context and typological characteristics. This study addresses this gap through a structured literature review of recent scientific publications, aiming to map and categorise climate-sensitive retrofit strategies across different building typologies. The methodological approach involves a qualitative synthesis of peer-reviewed studies, with interventions classified based on climate zone and building use. The results highlight the prevalence of envelope-related measures—such as thermal insulation and high-performance glazing—in residential and educational buildings, particularly in colder climates. Conversely, HVAC upgrades and passive solutions dominate in hot and mixed zones. The findings provide an evidence-based reference for stakeholders involved in designing renovation strategies, while also identifying the need for more context-aware, integrative frameworks that account for climate, building use, and socio-economic factors in retrofit decision-making.

1. Introduction

In recent years, rapid population growth and economic development have significantly increased global energy demand, with the building sector being one of the primary contributors. In Europe, the majority of buildings are over 50 years old [1], and the age of the global building stock is similarly alarming. As a result, most buildings remain energy inefficient, accounting for a large share of total electricity consumption. According to the International Energy Agency (IEA), buildings are responsible for approximately 40% of global energy consumption and 36% of greenhouse gas emissions [2]. This makes the building sector a priority area for emission reduction efforts and a key pillar in achieving global climate targets. Compared to other sectors such as transport and industry, buildings offer a higher potential for energy savings [3].

Greenhouse gas emissions are directly linked to climate change and the increasing frequency of extreme weather events such as heatwaves and floods. The Paris Agreement, signed in 2015 by 195 countries, aims to limit the global temperature rise to 1.5 °C. Achieving this objective requires rapid reductions in emissions, with building renovations and energy efficiency playing a central role [4]. Improving the energy performance of buildings necessitates informed decision-making across technical, environmental, regulatory, and social dimensions. Decision support systems (DSS) can facilitate this process by evaluating the performance and cost-effectiveness of renovation strategies, reducing uncertainty and increasing transparency [5]. This study aims to further support such decisions, particularly in relation to climate and building typologies.

The demand for energy in the building sector continues to rise, driven by urbanisation and growing comfort needs. Most existing buildings were constructed before stringent energy codes were in place, and many will still be operational in 2050. Sustainable renovations can reduce energy use by up to 75% [6], with HVAC systems alone responsible for over 40% of energy consumption. Their upgrade, therefore, plays a crucial role in overall performance outcomes. EU directives such as the EPBD have set strict targets and require member states to strengthen their building codes and incentivise energy upgrades [7].

Due to global warming, cooling demand is rising rapidly. Overreliance on air conditioning contributes to increased fossil fuel consumption, higher energy costs, and additional emissions. Without intervention, emissions from buildings could double by 2030. Yet, the IPCC reports that available technologies could reduce building energy consumption by 30–50% without significant investment increases [7]. To achieve net-zero targets by 2050, CO₂ emissions must be cut by 45% by 2030, with energy-efficient building interventions playing a decisive role [8].

Despite the critical importance of energy renovation, there remain several challenges in the literature. While numerous studies address building retrofitting, most focus solely on modelling and simulation rather than real-world implementations. This limitation hampers our understanding of the actual effectiveness of various interventions, as simulation-based projections may not reflect real-life performance [3]. Moreover, significant gaps exist in the context of regions such as the Middle East, where even theoretical investigations into energy retrofitting remain limited.

In addition, while many studies consider the technical and economic dimensions of energy upgrades, relatively few integrate the influence of climatic conditions and building typology in a systematic way. This is particularly important given that interventions effective in one climate zone or building type may underperform or even backfire in another. Furthermore, misconceptions persist—for example, that Southern European buildings primarily require cooling—overlooking the trade-offs with winter heating demand and the need for balanced strategies [8].

This paper aims to contribute to the growing body of knowledge by conducting a systematic literature review that explores the interplay between building renovation strategies, climate zones, and building typologies. The review aggregates and analyses existing evidence to derive a clearer understanding of how interventions perform under different climatic conditions and use cases (e.g., residential, commercial, historical buildings). The key objectives are as follows:

• To classify energy renovation interventions according to climate zone and building typology.
• To identify which strategies are most appropriate for each context.
• To provide a consolidated guide for stakeholders involved in building upgrades.
• To highlight areas where further empirical research is needed, especially in underrepresented regions.

While HVAC systems constitute a significant contributor to building energy consumption and are therefore discussed in this review, the study adopts a holistic perspective. It systematically analyses a wide range of retrofit strategies, including envelope insulation, glazing, shading, renewable energy integration, lighting, and advanced control systems, ensuring that findings are not limited to HVAC-related interventions.

The insights gained from this review are intended to inform policy, design, and investment decisions and support the transition to a decarbonised and climate-resilient building stock.

2. Theoretical Background

2.1. Climate and Energy Performance

Climatic conditions vary significantly across the globe depending on geographic location. As a result, regions are grouped into distinct climate zones, which influence both the design of buildings and the selection of appropriate renovation strategies. Based on the literature reviewed, four (4) major climate categories emerge, collectively covering the majority of inhabited areas worldwide [9]. These categories include the following:

(a)

Warm climates, both dry and humid, characterised by year-round high temperatures.

(b)

Cold and very cold climates, where low temperatures dominate, particularly in winter.

(c)

Continental climates, with hot summers and cold winters.

(d)

Temperate (Mediterranean) climates, marked by mild and balanced seasonal variations.

2.1.1. Warm Climates

Warm and tropical climates attract particular attention due to their unique challenges. Dry, hot regions are defined by consistently high temperatures, strong solar radiation, and minimal precipitation. Average temperatures typically range between 20 °C and 30 °C, with minor variations even during the night. These climates exhibit limited seasonal contrast, and water scarcity is a persistent issue.

However, not all warm climates are dry. Tropical regions—such as Southeast Asia and the Amazon Basin—combine high temperatures with elevated humidity and frequent rainfall, creating environmental conditions very different from those in arid areas like North Africa or the desert zones of the Middle East.

Warm climates are typically located near the equator and at low latitudes, including regions in Africa, South Asia, the Middle East, and Latin America. Some of these areas face extreme heat and drought, which limits vegetation and agricultural productivity, while others support rich biodiversity due to their humid tropical nature [10].

The impact of such climates on human life varies depending on the exact sub-type. Common features include extended periods of sunshine and warm weather, which can support tourism and certain crops. However, prolonged heat and water scarcity in arid climates can hinder habitation, strain ecosystems, and complicate building operation. For these reasons, selecting climate-appropriate retrofit strategies becomes vital. Buildings in such regions must ensure indoor thermal comfort by lowering internal temperatures, limiting solar heat gains, and preserving air quality—all while minimising energy consumption and environmental burden.

2.1.2. Cold and Very Cold Climates

Cold and very cold climates are found in high-latitude or high-altitude regions, including parts of Northern and Central Europe, Russia, northern China, Canada, and mountain ranges such as the Himalayas and the Alps. These areas are characterised by extremely low winter temperatures, often below freezing, with snow and frost being regular occurrences.

Very cold zones—such as the Arctic and high mountainous regions—experience average summer temperatures between −10 °C and 5 °C, with much harsher conditions in winter. Some of these regions, like Antarctica, are excluded from this study due to minimal human activity and infrastructure.

The challenges posed by these climates include long winters, limited sunlight, and restricted vegetation. Daily life is heavily influenced by weather severity, and energy needs are dominated by space heating and hot water provision. In such contexts, energy renovations must focus on minimising heat loss, ensuring airtightness, and improving insulation to reduce operating costs and dependency on fossil fuels.

2.1.3. Hot-Summers–Cold-Winters (Continental Climates)

Continental climates, characterised by hot summers and cold winters, present one of the most demanding contexts for building renovation. Although geographically less widespread, these climates entail high seasonal temperature swings. Summer periods are marked by strong solar radiation and high temperatures (often above 30 °C or even 40 °C), while winters bring significant drops, with values falling well below 0 °C [11].

Such climates are prevalent in inland regions of Central Asia (e.g., parts of China and Tibet) and North America, far from the moderating influence of large bodies of water. The intense thermal variation requires buildings to perform effectively across both extremes—offering adequate insulation and airtightness in winter, while also enabling cooling and solar protection in summer [12].

Older buildings in these zones often suffer from thermal inefficiencies due to outdated construction practices. Retrofitting efforts in such climates must be dual-purpose—improving both heating and cooling performance—and are typically more complex and costly. As such, they highlight the need for integrated renovation strategies that account for seasonal extremes, energy resilience, and indoor comfort.

2.1.4. Temperate and Mediterranean Climates

Temperate climates, including the Mediterranean subtype, are characterised by moderate temperatures and relatively stable seasonal patterns. These climates dominate many areas north and south of the tropics, including Southern Europe, parts of Western North America, Chile, South Australia, and regions of Northern Africa.

In temperate zones, winters are typically mild and summers warm but not extreme, with summer temperatures usually below 30 °C. Rainfall is more frequent in spring and autumn, and less common in summer. Mediterranean climates are a subtype of this category, noted for hot, dry summers and mild, wet winters—conditions common in Greece, Italy, Spain, and parts of the Middle East.

These climates are often seen as ideal for habitation and agriculture, offering balanced temperature and humidity profiles that support biodiversity and human activity. However, summer droughts and rising temperatures pose increasing risks, including water scarcity and wildfires.

Even though these climates are less extreme than others, the buildings in such areas still require context-sensitive renovation. Energy retrofits should aim to maintain thermal comfort during summer while minimising cooling loads, often through passive measures such as natural ventilation, external shading, and the use of reflective materials. Moreover, Mediterranean buildings must be resilient to climate change impacts, such as rising summer temperatures and increased energy demand for cooling.

Figure 1 (and Figure S1) presents the 4 climate zones as presented in previous subsections.

2.2. Building Typologies and Retrofit Needs

To support this comparative analysis, buildings are classified into four major categories:

(a)

Residential buildings.

(b)

Public and community buildings.

(c)

Commercial and office buildings.

(d)

Historical and traditional buildings.

This classification enables the identification of distinct retrofit needs, functional characteristics, and architectural constraints associated with each building type, thus facilitating the selection of appropriate energy renovation strategies.

2.2.1. Residential Buildings

Residential buildings are designed to accommodate individuals and families, comprising the largest share of the global building stock [13]. Their architectural and construction characteristics vary significantly depending on user needs, cultural factors, and climatic conditions. These buildings typically include bedrooms, kitchens, bathrooms, living areas, and, in some cases, workspaces. The layout and size are influenced by housing type and household composition.

Essential features of residential buildings include structural integrity, energy efficiency, and safety. Architecturally, they range from conventional designs to contemporary layouts, with form often shaped by cultural and socioeconomic parameters. In recent years, sustainability and energy performance have become dominant priorities, encouraging the use of renewable energy systems and environmentally friendly materials.

Designing climate-adapted residential buildings involves selecting high-quality materials that ensure thermal insulation, soundproofing, and weather resistance. This approach helps maintain indoor thermal comfort despite external temperature variations. Renovation of residential stock is particularly pressing in regions with extreme climates, where ageing buildings often fall short of modern energy and comfort standards [14]. Retrofitting efforts typically focus on enhancing energy performance, thermal comfort, and affordability, aiming to reduce energy expenses while improving quality of life.

2.2.2. Public and Community Buildings

Public and community buildings are critical components of urban infrastructure, housing essential services and facilities for the general population. Public buildings include schools, hospitals, administrative services, courthouses, museums, and libraries. Their design prioritises functionality, safety, and inclusivity, ensuring access for all users, including individuals with mobility limitations.

Community buildings serve broader social purposes, often hosting activities that promote cohesion and collective well-being. These include health centres, social support hubs, cultural centres, gyms, and shelters. Flexibility and spaciousness are key architectural priorities, allowing for the accommodation of diverse activities and large numbers of users.

In both public and community buildings, durability and accessibility are essential. Construction typically adheres to strict safety regulations, and materials are selected to ensure long-term resilience. Many of these buildings integrate large open spaces and shared facilities to handle high visitor volumes. Increasingly, public infrastructure serves as a model of environmental leadership, adopting renewable energy technologies and energy-efficient systems.

However, financial viability often remains a challenge, especially in community buildings supported by non-profit organisations or volunteer groups [15]. As such, renovation measures must not only improve energy performance but also maintain affordability and ensure ongoing service delivery. Retrofitting these buildings contributes to user comfort, reduces operational costs, and ensures resilience against climate impacts—thus preserving their critical role in urban society.

2.2.3. Commercial and Office Buildings

Commercial and office buildings form the backbone of economic activity in urban areas. Commercial spaces include shops, restaurants, supermarkets, and shopping centres, generally located in central districts or commercial zones. Office buildings host businesses and professionals, often in high-rise or multi-storey layouts, with shared meeting areas, amenities, and ICT infrastructure.

The design of office buildings balances functionality with visual identity. Large corporations often seek to reflect corporate branding through distinctive architectural choices. However, these aesthetic elements—especially glass façades and expansive glazing—can negatively affect energy efficiency [16]. Many such buildings were designed before energy codes were enforced, without consideration for environmental impact.

Commercial buildings typically prioritise accessibility and visibility, featuring large glass frontages and open interiors. In contrast, the focus in office buildings is on internal layout and comfort, which influences lighting, HVAC design, and ventilation systems. Both types increasingly adopt sustainability practices, integrating renewable energy and high-efficiency systems—often as part of corporate social responsibility strategies.

Given their large scale, complete reconstruction of commercial and office buildings is rarely feasible. As a result, energy retrofits are favoured. Interventions in these buildings aim to reduce energy demand, maintain indoor comfort, and mitigate exposure to extreme weather conditions. This is particularly urgent for buildings with outdated glass façades or in regions with severe temperature fluctuations.

2.2.4. Historical and Traditional Buildings

Historical and traditional buildings are integral to a region’s cultural identity, representing architectural, artistic, and societal values from past eras. These structures include religious sites, mansions, public halls, and vernacular dwellings, often constructed with locally sourced materials such as wood, stone, and brick. They not only serve as living historical artefacts but also contribute to cultural tourism and local economies.

Preserving the architectural integrity of such buildings is vital, yet challenging, especially in the face of urban development and natural degradation. Retrofitting efforts must strike a balance between enhancing functionality and maintaining historical authenticity [17]. Renovations typically involve the use of traditional materials and methods, alongside careful integration of modern systems for energy efficiency, safety, and comfort.

Due to legal protections and heritage regulations, interventions must comply with strict guidelines that prevent irreversible alterations to historic features. The aim is to prolong the lifespan of these buildings, adapt them to modern usage, and improve their environmental performance. When sensitively implemented, retrofits of historical buildings offer a unique opportunity to bridge cultural preservation with contemporary sustainability goals.

It is acknowledged that data centres represent a rapidly growing share of global energy demand—currently estimated at around 2% due to the increasing computational requirements of AI and cloud services. However, these facilities were excluded from the scope of this review, as their energy consumption patterns, cooling requirements, and operational profiles differ substantially from typical residential, commercial, and public buildings analysed in retrofit-focused studies.

2.3. Common Retrofit Strategies

Energy renovation strategies are selected according to the building typology, climatic conditions, and performance objectives. Despite the diversity of retrofit interventions, certain categories appear consistently across the literature and in practice. These commonly implemented strategies aim to reduce operational energy use, improve thermal comfort, and increase the overall efficiency of buildings.

2.3.1. Thermal Insulation and Envelope Upgrades

One of the most prevalent retrofit measures involves improving the thermal performance of the building envelope. This typically includes the addition of insulation to external walls, roofs, and, in some cases, floors. Enhancing the envelope’s thermal resistance minimises unwanted heat transfer between indoor and outdoor environments, reducing the need for heating or cooling depending on the season [18].

Window replacement or retrofitting is also frequent, often involving the installation of double or triple glazing, low-emissivity (low-e) coatings, or insulated frames. These upgrades reduce thermal losses, improve airtightness, and prevent discomfort from cold surfaces or drafts [19]. External or internal shading systems are sometimes used in warm climates to reduce solar heat gains.

2.3.2. HVAC and System Efficiency Improvements

Heating, ventilation, and air conditioning (HVAC) systems account for a significant proportion of building energy use [20]. Retrofit strategies frequently include the replacement of outdated boilers, chillers, and air handling units with modern, high-efficiency alternatives. In many cases, heat pumps are introduced, as they offer both heating and cooling capabilities with reduced energy consumption and lower carbon emissions.

Additionally, mechanical ventilation systems with heat recovery are often employed, particularly in cold climates, where maintaining indoor air quality without excessive heat loss is essential [21]. The integration of building automation and control systems can further enhance energy performance by regulating temperature, humidity, and lighting in response to occupancy and external conditions.

2.3.3. Lighting and Appliance Upgrades

The replacement of lighting systems with LED technology is one of the most cost-effective retrofit measures. These upgrades are applicable across building types and climates, offering immediate reductions in electricity consumption and maintenance costs [22]. In non-residential buildings, lighting controls such as occupancy sensors and daylight dimming are often integrated to optimise performance [23].

Similarly, replacing outdated appliances and plug-load equipment with energy-efficient alternatives can significantly lower energy demand in residential and commercial settings. In office buildings, ICT equipment is often targeted for replacement or management via smart systems to reduce standby and peak load consumption.

2.3.4. Integration of Renewable Energy Systems

In many renovation projects, on-site renewable energy generation is introduced to reduce reliance on fossil fuels and lower carbon emissions. Solar photovoltaic (PV) panels are the most widely implemented solution, particularly in climates with high solar irradiance [24]. In some cases, building-integrated photovoltaics (BIPV) are used to combine architectural and energy functions.

Other technologies such as solar thermal collectors, small-scale wind turbines, and biomass boilers may also be considered depending on local context and energy needs. These systems are usually supported by storage solutions and smart meters to manage energy production and consumption effectively [25].

2.3.5. Passive Design Strategies and Behavioural Adaptation

Passive design principles aim to reduce energy consumption through architectural design without relying on active systems. Common interventions include the optimisation of building orientation, use of natural ventilation, thermal mass exploitation, and strategic shading. These measures are particularly relevant in climates with moderate seasonal variations and are often applied during deep renovation projects.

In parallel, occupant behaviour plays a crucial role in the success of retrofit measures. Educational campaigns, user-friendly control interfaces, and feedback systems can support more energy-conscious usage patterns, helping to maximise the impact of physical upgrades.

2.4. Review of Relevant Works

In this review, we adopted a structured synthesis approach, organising the literature according to climate zones and building typologies. This dual classification allows us to compare retrofit strategies across environmental contexts and functional building categories, ensuring that findings are systematically analysed rather than presented chronologically.

While several recent reviews have analysed retrofit strategies either by climate or by building typology, to the best of our knowledge, no existing study has systematically integrated both dimensions into a single comparative framework. This creates a gap in understanding how retrofit measures interact with both environmental and typological factors simultaneously.

The recent literature has increasingly emphasised the significance of climate zones and building typologies as key determinants for effective retrofit strategies. Several systematic reviews published since 2020 have aimed to categorise retrofit approaches by climate and building use, offering global insights into best practices and existing challenges. For example, Bjelland [26] presented a comprehensive review of single- and multi-building retrofitting projects across various regions, noting a pronounced increase in retrofit-focused research. However, they identified a marked bias towards European contexts and residential buildings, with many climate zones—particularly those outside temperate Europe—remaining insufficiently studied. Bjelland and colleagues further highlighted that retrofit findings are only partially transferable between climate zones, thus calling for internationally unified frameworks and a broader inclusion of non-residential “lighthouse” buildings.

Shen [27] contributed a synthesis of recent developments in climate-adaptive retrofitting, underscoring the variability in retrofit performance under future climate scenarios. They demonstrated that passive measures, such as insulation and natural ventilation, may lose effectiveness in certain regions as global temperatures rise. Their work advocates for tighter integration of climate models with building simulations and the use of downscaled climate data to enhance local relevance. Furthermore, Shen point to the growing use of multi-objective optimisation and decision-support tools that enable the tailoring of retrofit solutions not only for immediate energy performance but also for long-term resilience.

Tajuddeen and Sajjadian [28] provided a global review of climate-responsive retrofit strategies in the built environment, reaffirming the prominence of passive solutions—especially when complemented by active systems for year-round effectiveness. Their analysis clearly demonstrates the climate-dependency of retrofit priorities, showing that cooling-focused interventions may be optimal in tropical zones, whereas heating demand reductions dominate in colder climates.

In addition to these high-level reviews, multiple studies have developed retrofit classifications based on regional or climatic considerations. A review of retrofit strategies in tropical climates, for instance, identified three dominant passive approaches: enhancing building envelope insulation, maximising natural ventilation, and incorporating shading devices. These measures mirror the recurring themes across other climates, suggesting that while retrofit principles may be universal, their implementation must be context-specific [29].

The literature also shows that the energy performance of identical measures—such as window upgrades—varies considerably depending on local climate conditions. A study from China [30], for example, revealed that optimal window technologies (e.g., glazing type, U-values, shading coefficients) must be selected with respect to regional climatic demands. Accordingly, many scholars advocate for retrofit guidelines and performance standards that are climate-zone-specific [27].

In parallel, building typology emerges as another crucial factor. While residential buildings remain the dominant focus of retrofit research, there is a growing recognition of the need to develop typology-specific strategies. Kaczmarek [31] focused on school buildings in cool-temperate climates and highlighted the importance of accounting for specific use patterns, such as classroom occupancy and indoor air quality. Similarly, Bencid [29] explored office buildings in tropical zones, showing that mechanical systems and smart controls yield greater energy savings than envelope upgrades in hot humid contexts. Their findings expose typological gaps in the literature, especially for non-residential and large-scale buildings.

Another key regional focus is the Middle East and other arid regions, where cooling loads dominate energy use. Kutty reviewed retrofit measures in Gulf countries [32], identifying high-performance insulation, thermal mass strategies, and solar shading as crucial for mitigating extreme cooling demands. These studies underline that building use and geographical setting jointly determine the efficacy of retrofit measures.

Moreover, simulation and optimisation tools are now widely employed to evaluate and refine retrofit interventions. A study demonstrated through parametric simulations across 25 climate zones that passive design effectiveness varies dramatically by location [29]. Similarly, Dehghan and Porras Amores employed a genetic algorithm to explore energy, cost, and comfort trade-offs in Middle Eastern retrofits. Their framework shows how multi-criteria optimisation can support climate-adapted and context-sensitive decision-making [33].

The research landscape has thus shifted towards more holistic and quantitative approaches to building retrofitting. Studies increasingly integrate performance metrics—such as thermal comfort, resilience, and cost-effectiveness—into multi-objective models, yielding tailored retrofit guidelines supported by software tools or decision matrices [34].

In addition, recent studies have also started incorporating multi-criteria decision-making (MCDM) and multi-stakeholder optimisation techniques to improve the prioritisation of retrofit strategies. For example, a study proposed an innovative multi-stakeholder decision methodology for optimising energy retrofits in shopping mall buildings, integrating technical, financial, and stakeholder-driven objectives to guide investment decisions [35]. Similarly, another recent work explored HVAC system retrofitting for a university lecture room, explicitly balancing private and public interests through a structured optimisation framework [36]. These studies illustrate an emerging trend towards using advanced decision support methods to classify and rank retrofit interventions. While the present review does not perform such multi-objective optimisation, it provides a foundational mapping of retrofit strategies across climate zones and building typologies that can complement and inform these prioritisation frameworks.

Despite these advances, several gaps remain unaddressed. The most prominent among them is the fragmented and uneven coverage of climates and building types the in existing literature. Many reviews are either region-specific or typology-limited, often concentrating on residential buildings in temperate climates. Moreover, existing studies seldom consolidate retrofit recommendations in a structured and comparative manner across both climatic zones and typological categories. Taken together, these studies provide valuable insights into climate-sensitive and typology-driven retrofitting. However, their findings remain fragmented, and no comprehensive mapping exists that jointly examines how retrofit strategies vary across both climate zones and building typologies.

This paper aims to fill this gap by presenting a structured review and synthesis of renovation strategies stratified by both climate zone and building typology. Unlike previous studies that focus on specific regions or building uses, this work provides a unified and comprehensive framework intended to guide retrofit interventions globally. By analysing multiple building types (residential, public, commercial, and historic) and aligning them with distinct climate classifications, the study offers targeted yet comparative insights that can inform policy, practice, and future research across diverse contexts. Therefore, this paper directly addresses this gap by presenting the first structured and comparative synthesis of retrofit strategies jointly classified by climate zone and building typology. By doing so, it identifies emerging patterns that would remain invisible in single-dimensional analyses, offering a global framework to guide retrofit interventions across diverse contexts.

3. Methodology

This study adopts a structured review approach to analyse how building retrofitting strategies vary across different climate zones and building typologies. The objective is to synthesise findings from recent research, identify patterns and commonalities, and highlight differences in retrofit practices under distinct climatic and functional contexts. To ensure scientific rigour and reproducibility, the methodology was designed following systematic review principles, drawing inspiration from the PRISMA 2020 guidelines.

The review process was divided into four stages:

• Defining the research scope and keywords.
• Performing a structured literature search.
• Applying inclusion and exclusion criteria.
• Extracting and categorising data.

3.1. Search Strategy

An extensive literature search was conducted in Google Scholar and Scopus, which are widely acknowledged as comprehensive databases for scientific publications. The search was initially conducted for studies published between January 2019 and December 2024 and was updated in August 2025 to capture the most recent developments in the field. The update yielded no additional eligible studies, confirming the completeness of the dataset.

To ensure a comprehensive collection of relevant studies, broader and standardised search terms were defined, combining three main concept groups: retrofit, climate, and building typology. Boolean operators (AND, OR) were used to generate combinations, as summarised below in

Table 1. Search concepts and keywords.

Concept	Search Terms Used	Rationale
Retrofit focus	“building retrofit” OR “building renovation” OR “building refurbishment” OR “energy upgrade”	Captures different terms used globally
Climate focus	“climate zone” OR “climatic region” OR “climate-adaptive” OR “climate-sensitive”	Ensures inclusion of climate-contextual studies
Typology focus	“residential buildings” OR “public buildings” OR “educational buildings” OR “commercial buildings” OR “historic buildings” OR “office buildings”	Covers diverse building categories

:

3.2. Inclusion and Exclusion Criteria

To guarantee the quality and relevance of the selected studies, explicit inclusion and exclusion criteria were applied.

• Inclusion criteria
  • Peer-reviewed journal or conference papers.
  • Published between January 2019 and August 2025.
  • Studies explicitly linking retrofit strategies to climate zones, building typologies, or both.
  • Quantitative and qualitative studies using simulations, optimisations, or analytical frameworks.
• Exclusion criteria
  • Non-peer-reviewed sources (e.g., theses, reports, white papers).
  • Studies without explicit mention of climate classification.
  • Papers focusing on new construction rather than retrofit interventions.

This explicit filtering enhances transparency and aligns the methodology with good review practices.

3.3. Climate and Typology Classification

To enable structured cross-comparison, the selected studies were grouped into four climate categories based on established frameworks, including the Köppen–Geiger classification and the widely referenced retrofit literature [37]:

• Warm climates—dry or humid, characterised by year-round high temperatures.
• Cold and very cold climates—dominated by low temperatures, particularly in winter.
• Continental climates—experiencing hot summers and cold winters.
• Temperate climates (including Mediterranean regions)—mild and balanced seasonal variations.

Although alternative classifications, such as the ASHRAE climate zone methodology, provide greater regional granularity, we adopted the Köppen–Geiger framework combined with the widely referenced retrofit literature to ensure global applicability and maintain consistency with the majority of studies included in this review. This approach enables robust cross-comparisons across diverse geographic contexts without introducing regional bias.

This categorisation ensures consistency with global energy modelling practices and facilitates meaningful comparison of retrofit performance across diverse climatic contexts.

Similarly, buildings were classified into four typologies to account for differences in operational demands, retrofit needs, and architectural constraints:

• Residential buildings.
• Public and community buildings (e.g., schools, hospitals, municipal offices).
• Commercial and office buildings.
• Historical and traditional buildings.

This classification aligns with established international frameworks, such as TABULA/EPISCOPE, IEA Annex 75, and recent systematic reviews. It enables typology-specific comparisons and highlights distinct drivers influencing retrofit decisions, including the following:

• Occupancy schedules in public and educational buildings.
• Lighting and HVAC demands in commercial settings.
• Conservation and regulatory constraints in heritage properties.

To ensure consistency during the classification process, studies were first assigned to climate zones and building types based on the information explicitly reported by the authors. Where climate classifications were missing, the geographic location of the case study was cross-referenced with the Köppen–Geiger global database. Similarly, for building typologies, ambiguous cases (e.g., mixed-use buildings or multi-building case studies) were resolved by mapping each study to all applicable categories rather than forcing a single classification. This structured approach ensured systematic comparability of retrofit strategies across diverse climatic contexts and building types.

3.4. Study Selection and Categorisation

The initial search retrieved 712 records. The study selection process followed a structured two-phase approach to ensure relevance, transparency, and replicability. In the screening phase, all 712 records retrieved from the database search were assessed by reading titles and abstracts. Studies were retained if they met the following basic screening criteria:

• The title or abstract referred explicitly to building retrofitting, energy renovation, or refurbishment.
• The study mentioned any climatic or geographic context, even indirectly (e.g., by referencing location).
• The abstract indicated that the study focused on existing buildings, rather than new construction.

This initial screening yielded 134 studies eligible for full-text review.

In the selection phase, the full texts of the 134 studies were thoroughly reviewed using the inclusion and exclusion criteria outlined in Section 3.2. Studies were retained if they fulfilled the following:

• Explicitly linked retrofit strategies to at least one climate zone, building typology, or both.
• Reported quantitative or qualitative analysis, including simulation, optimisation, or decision support methods.
• Provided sufficient details on the retrofit interventions considered.

Articles were excluded if they lacked methodological detail, focused solely on material science or construction techniques without retrofit context, or did not distinguish between new builds and retrofitting. When geographic or climate information was not explicitly provided, it was inferred based on the case study’s location using the Köppen–Geiger classification. Similarly, for building typologies, classifications were made based on the described function and use patterns. Borderline cases were resolved through consensus among the authors. After applying these criteria, 55 studies were included in the final synthesis. Each selected study was systematically coded based on the following:

• Climate zone.
• Building typology.
• Retrofit measures investigated.
• Analytical or simulation approaches used.

This structured categorisation enabled the creation of comprehensive tables summarising the findings, facilitating a comparative assessment of retrofit measures across climates and typologies. The resulting dataset forms the foundation for the analysis presented in Section 4. Figure 2 depicts the literature selection methodology of our work.

As previously mentioned, one of the primary inclusion criteria was the publication date of the study. The temporal distribution of selected works is illustrated in Figure 3.

Another key criterion concerned the credibility and academic rigour of the publishing source. The overwhelming majority of the selected studies (54 out of 55), as depicted in Figure 4, were published in peer-reviewed scientific journals, such as Energies, Sustainability, and Buildings. One study, titled “A systematic review of retrofitting tools for residential buildings,” was sourced from a reputable conference proceedings collection.

The principal thematic criterion for inclusion was a focus on energy renovation of buildings across varying climatic conditions. The selected publications examined parameters such as building type and climate and how these influence recommended retrofit interventions and outcomes. Although economic aspects were sometimes considered in these studies, they were not primary selection criteria.

To support a comprehensive analysis, the study intentionally included a wide range of building types and climate conditions. Some publications were excluded due to saturation on a specific climate or building category. No exclusions were made based on geographic location or the nationality of the authors.

The final set of studies examined retrofitting interventions targeting both the building envelope and interior systems. These studies evaluated the effectiveness of such measures in terms of energy efficiency improvement, carbon footprint reduction, initial investment cost, and payback periods. Each selected paper was catalogued in

Table A1. List of reviewed studies.

ID	Title	Year	Problem	Renovation Activities	Technical Approach	Journal
1 [6]	Study on performance of energy-efficient retrofitting measures on commercial building external walls in cooling-dominant cities	2013	Cooling, dominant cities, energy consumption	Building envelope retrofitting, retrofitting measures on building facades	External and internal insulation, high-reflectivity coating	Applied Energy
2 [12]	Building Energy Retrofit Measures in Hot-Summer–Cold-Winter Climates: A Case Study in Shanghai	2019	Hot-summer–cold-winter climates, energy consumption	Building envelope, equipment system, renewable energy, energy-conserving behaviours, control systems, ventilation	Insulation, cool roofs and coatings, control upgrade, lighting upgrade, thermal storage and heat recovery, solar PV/PVT systems, solar thermal systems, biomass systems, geothermal systems, wind power systems	Energy
3 [41]	Retrofitting towards energy-efficient homes in European cold climates: a review	2019	Cold climates, energy consumption, carbon emissions	Building envelope, airtightness, HVAC, on-site energy sources, ventilation, lighting and electrical appliances, building control systems, user interaction	Heat pumps, combined heat and power, thermal insulation, glazing windows, thermal bridges, thermal energy storage, ventilation with heat recovery, intelligent control	Energy efficiency
4 [46]	A review of retrofit interventions for residential buildings in hot humid climates	2020	Hot climates, energy consumption	Renewable energy systems, building envelope, “umbrella concept”, ventilation	Insulation, thermal mass materials, reflective insulation material (radiant barrier), green/white roofs, ventilated roofs, natural ventilation, (filled with gas) double/triple glazing, low emittance coating on glass, electrochromic glazing system, shading devices like vertical fins, window reveals and overhangs, wind energy, solar PVs	International Journal of Environmental Science and Development
5 [52]	Feasibility and retrofit guidelines towards net-zero energy buildings in tropical climates: A case of Ghana	2022	NZEB, tropical climates	Enhance daylight, ventilation, improve envelope, energy-efficient air-conditioning and lighting, solar energy	Light-coloured and cool roofs, air conditioner or heat pump, solar PV, sensors, mechanical ventilation, intelligent BMS	Energy and Buildings
6 [48]	A Critical Review of Facade Retrofit Measures for Minimizing Heating and Cooling Demand in Existing Buildings	2021	Minimise cooling and heating demand through insulation	Building envelope	Wall and window insulation, glazed windows	Science of the Total Environment
7 [53]	Decision methodology for the development of an expert system applied in an adaptable energy retrofit facade system for residential buildings	2015	Performance improvements, coordination with the current regulations	Building envelope	Wall insulation, DSS, air-conditioning replacement	Renewable Energy
8 [54]	Retrofitting High-Rise Residential Building in Cold and Severe Cold Zones of China–A Deterministic Decision-Making Mechanism	2020	Decision-making mechanism for finding the optimum retrofit solutions	Solar energy, building envelope, HVAC improvements	Wall and ground insulation, PVCs, HAC replacement, LED, shades as shelves, thermostat	Sustainability
9 [55]	Building retrofitting towards net zero energy: A review	2024	Retrofit measures towards NZEB	Renewable energy systems, HVAC improvements	Solar panels, wind turbines, geothermal energy, HVAC upgrade, triple-glazed windows	Energy and Buildings
10 [56,57]	Climate adaptation of existing buildings: A critical review on planning energy retrofit strategies for future climate	2024	Reducing environmental impacts and costs	Building envelope, air-conditioning replacement	Insulation, air-conditioning, solar energy systems, renewable energy systems, ventilation improvement	Renewable and Sustainable Energy Reviews
11 [57]	A Data-driven Approach for Sustainable Building Retrofit–A Case Study of Different Climate Zones in China	2020	Dominant energy needs in five different climatic zones	Building envelope, HVAC and lighting improvements	External insulation improvement, window replacement with high-efficiency glass, HVAC replacement, LED, BMS	Sustainability
12 [58]	A Multi-Facet Retrofit Approach to Improve Energy Efficiency of Existing Class of Single-Family Residential Buildings in Hot-Humid Climate Zones	2020	Hot-humid climates, potential energy savings	HVAC replacement	Heat pump HVAC system improvements, LED, solar systems, BMS	Energies
13 [59]	The Implications of Climate Zones on the Cost-Optimal Level and Cost-Effectiveness of Building Envelope Energy Renovation and Space Heat Demand Reduction	2017	Climate zones, cost-optimal residential-level building	Building envelope, HVAC	HVAC improvements, external insulation and wall upgrades, shades, green roofs and rain water collection	Buildings
14 [8]	Energy performance analysis of alternative building retrofit interventions for the four climatic zones of Greece	2024	Greek climatic zones, improvement of the building’s energy performance	Building envelope, insulation, mechanical ventilation	External wall insulation, rooftop PCM integration, mechanical ventilation system with summer operation, rooftop cool coating application, heat pumps	Journal of Building Engineering
15 [17]	Identifying practical sustainable retrofit measures for existing high-rise residential buildings in various climate zones through an integrated energy-cost model	2021	Energy–cost model retrofit measures based on climates, building features and retrofit cost	Building envelope, window and HVAC replacement, solar energy systems	Wall and roof insulation, double/triple-glazed windows, heat pumps, HVAC replacement, LED, PVCs for energy and hot water production, BMS, mechanical ventilation with heat recovery, external shades	Renewable and Sustainable Energy Reviews
16 [7]	Energy retrofit optimization for social building in temperate climate zone	2022	Social housing, reduction in the emission of greenhouse gases, comfortable temperature	Hybrid generation system, control systems	Hybrid heat-pump–natural-gas-boiler system, on–off air-to-water heat pump, thermostat	Energy and Buildings
17 [51]	Energy Retrofitting Assessment of Public Building Envelopes in China’s Hot Summer and Cold Winter Climate Region	2022	HSCW, save energy and reduce carbon emissions	Building envelope insulation, window replacement	Insulation layer inside the external wall, low-E glassing windows, partial horizontal and vertical green roof and wall	Buildings
18 [60]	Upgrading the Smartness of Retrofitting Packages towards Energy-Efficient Residential Buildings in Cold Climate Countries: Two Case Studies	2020	Building automation control strategies	Building envelope, automation systems, heating system replacement	BMS for heating, ventilation, lighting, hot water, external insulation, air/water heat pumps	Buildings
19 [61]	Energy, carbon, and cost analysis of rural housing retrofit in different climates	2020	Energy and cost-effective retrofit strategies, four climates	Building envelope, heating system replacement, solar energy systems	Wall, roof and ground insulation, high efficiency heating systems, PVCs for energy and hot water production, shades	Journal of Building Engineering
20 [45]	Exploring the effects of a building retrofit to improve energy performance and sustainability: A case study of Korean public buildings	2019	Public building, green remodelling	Building envelope, HVAC, plug loads, lighting, and renewable energy	Insulation, relocating and replacing windows with triple-glazed low-e Argon, high efficiency doors, electric heat pumps (EHP), on/off control of office equipment, LED lighting, on/off sensors, PV panels, inverted roof component system	Journal of Building Engineering
21 [62]	Energy retrofits in historic and traditional buildings: A review of problems and methods	2017	Criteria, analysis methods, and decision-making processes	Building envelope, HVAC and window replacement, renewable energy	Wall and roof insulation, high efficiency heating systems like heat pumps, glazed windows, external shades	Renewable and Sustainable Energy Reviews
22 [63]	A cost-effective building retrofit decision-making model–Example of China’s temperate and mixed climate zones	2020	Sustainable building retrofitting, NPV	Building envelope, HVAC replacement, lighting	Wall and roof insulation, heat pumps, ventilation upgrade, LED, shades	Journal of Cleaner Production
23 [64]	Retrofit strategies to improve energy efficiency in buildings: An integrative review	2024	Natural resources and suitable conditions, different climates	Building envelope, renewable sources	Improvement of HVAC, water heating and light systems, insulation, phase change materials, ventilation, green façade, green roof and cold roof, rational use of water	Energy and Buildings
24 [65]	Analysis of energy economic renovation for historic wooden apartment buildings in cold climates	2014	Energy consumption and potential energy savings	HVAC systems, airtightness, windows	External insulation, mechanical ventilation with heat recovery, double-glazed windows, heating system improvements	Applied Energy
25 [66]	Towards Nearly-Zero Energy in Heritage Residential Buildings Retrofitting in Hot, Dry Climates	2021	Evaluation of the potential of turning heritage building stock into NZE, hot, dry climates	Building envelope, lights, solar energy, ventilation upgrade	Wall and roof insulation, PVCs, solar thermal systems, LED, BMS, mechanical ventilation	Sustainability
26 [49]	Optimization of Thermal Behavior and Energy Efficiency of a Residential House Using Energy Retrofitting in Different Climates	2020	Strategies and potentials of energy savings	Building envelope, HVAC, windows	HVAC upgrade and heat pumps, wall and roof insulation, BMS, window replacement	Civil Engineering and Architecture
27 [67]	Simplified Guidelines for Retrofitting Scenarios in the European Countries	2023	European countries, priority scenarios	Building envelope, VAC systems, solar energy	Window and AC replacement, insulation, PVCs, mechanical ventilation	Energies
28 [68]	Assessment of Passive Retrofitting Scenarios in Heritage Residential Buildings in Hot, Dry Climates	2021	Indoor thermal comfort, passive retrofitting	Building envelope, solar energy	Insulation upgrade, solar heating and AC systems, ventilation upgrade, shades	Energies
29 [69]	Exploring Energy Retrofitting Strategies and Their Effect on Comfort in a Vernacular Building in a Dry Mediterranean Climate	2023	Optimal passive strategies for rehabilitating a traditional house	Building envelope, ventilation upgrade	Insulation, window size, ventilation with fans, shades	Buildings
30 [70]	BIM-based techno-economic assessment of energy retrofitting residential buildings in hot humid climate	2020	Techno-economic feasibility of retrofitting	Building envelope, HVAC, lighting, renewable energy	HVAC, insulation and window upgrade, LED, PVCs, shades	Energy and Buildings
31 [71]	Building glass retrofitting strategies in hot and dry climates: Cost savings on cooling, diurnal lighting, color rendering, and payback timeframes	2021	Glazing retrofit, air-conditioning cost saving, payback period, hot climates	Various retrofitting glazing arrangements, thermal/solar transmittance	Multi-panes, insulation, PCMs, low-e double-glazing units, hydrogels, PVCs, solar control layers, electrochromic smart windows, stained/reflective/tinted/clear texture brick glasses, laminated glazing system, film of micro-sized liquid crystal molecules	Energy
32 [72]	A review of Building Energy Retrofit Measures, Passive Design Strategies and Building Regulation for the Low Carbon Development of Existing Dwellings in the Hot Summer–Cold Winter Region of China	2023	Low carbon future, hot-summer–cold-winter climates, residential building	Building envelope, solar heating and electricity, smart control/management technologies, active cooling and heating	Sun-shading windows, triple-glazed windows, high-performance windows, radiative cooling, solar chimney, insulation	Energies
33 [73]	Energy-Efficient Window Retrofit for High-Rise Residential Buildings in Different Climatic Zones of China	2019	Window retrofit, different climates	Window glazing, window–wall ratio, window direction, coating, light reflection, thermal transmittance, air sealing	Light-coloured zones, thermo-chromic glazing, tinted glass, single/double-glazed windows, low-e glass, electrochromic	Sustainability
34 [74]	Energy Retrofitting Technologies of Buildings: A Review-Based Assessment	2023	Energy consumption	Building envelope, HVAC, lighting, renewable energy	Insulation, shading devices, green walls, low-emissivity glazing, ventilation systems, split AC, solar AC, hybrid AC, LED, lighting control, sensors, photovoltaics, wind turbines	Energies
35 [40]	Potential retrofits in office buildings located in harsh Northern climate for better energy efficiency, cost effectiveness, and environmental impact	2022	Commercial building, harsh climate-energy consumption and greenhouse gas emission reduction	Building envelope, water heating system, airtightness, renewable energy system	Increasing wall and roof thermal insulation, HVAC system, replacing the old hot water boiler, argon-filled double glass windows, solar thermal heating and electricity generation using photovoltaics	Process Safety and Environmental Protection
36 [43]	Retrofit Analysis of City-Scale Residential Buildings in the Hot Summer and Cold Winter Climate Zone	2023	HSCW, air-conditioner control, payback period	Diverse AC operation strategies, lighting system upgrades	EPS material for renovation of exterior walls and roofs, new window structures, vertical overhangs for external shading, air sealing, low-e glass	Energies
37 [44]	Optimal energy retrofit plan for conservation and sustainable use of historic campus building: Case of cultural property building	2020	Low energy performance and conservation of cultural/historical wooden building	Passive, active, and renewable energy technologies (BER3)	Roof and wall insulation, low-e double glazing and low-e triple glazing windows with a polyvinyl chloride (PVC) frame, LED lights, internal blinds, infiltration, PVS panels, high-efficiency HVAC system, exterior overhangs	Applied Energy
38 [50]	Innovative technologies for energy retrofit of historic buildings: An experimental validation	2018	Historical buildings, lower energy consumption and increase comfort	HVAC systems and control strategies	Surface Water Heat Pump (SWHP), Demand Controlled Ventilation (DCV), trigeneration, building management system (BMS)	Cultural Heritage
39 [75]	Net-zero energy retrofit of rural house in severe cold region based on passive insulation and BAPV technology	2022	Non-renewable resources and carbon emissions reduction-rural houses	Building envelope, PV system	High thermal insulation foaming cement, PV panels on the roof and facades	Journal of Cleaner Production
40 [76]	Advanced Decision–Making Framework for Sustainable Energy Retrofit of Existing Commercial Office Buildings	2024	Life-cycle cost analysis, economic valuation, multi-criteria decision analysis tools and criteria, commercial building	HVAC system upgrade, window replacement, lighting retrofit, insulation improvement, solar power	High-efficiency variable refrigerant flow (VRF) system, double-glazed single low-e glass on doors and windows, LED lighting systems with proper controls, insulation of walls and roofs, solar panels	International Journal of Scientific Research and Management
41 [3]	Commercial building retrofitting: Assessment of improvements in energy performance and indoor air quality	2021	Energy efficiency, indoor environmental quality, energy savings, cost	Thermal comfort, lighting, noise control, building envelope insulation, HVAC improvement, operational schedule	Thermal insulation of roof, walls and windows, double-glazed windows tinted with low-e coating and reflective coating, LEDs, HVAC system improvements, change thermostat setpoint	Construction and Site Management
42 [77]	Envelope retrofitting strategies for public school buildings in Jordan	2019	Envelope retrofitting, uninsulated buildings	Building envelope, mechanical system upgrade, electrical system retrofitting	Wall, roof, window insulation, roof reflectance, reduced air leakage, heat recovery ventilation, shades like horizontal overhangs	Journal of Building Engineering
43 [47]	Energy and economic analysis on retrofit actions for Italian public historic buildings	2019	Historic (public) building-effectiveness of national measures, four different climatic zones of Italy	Building envelope, lighting, solar system	Internal thermal insulation, roof insulation, shading devices, window substitution, LED, lighting control system, PV system	Energy
44 [5]	A Review of Energy Efficiency Interventions in Public Buildings	2023	Different types of public buildings, energy efficiency, carbon footprint reduction	Building envelope, lighting, HVAC	Insulation, HVAC improvement, LED lights, solar heating systems, BMS, PV, public awareness	Energies
45 [78]	Guidelines, barriers and strategies for energy and water retrofits of public buildings	2018	Scenario modelling, stakeholder workshops, interviews	Building envelope, lighting, HVAC, renewable energy	New HVAC systems, insulation of walls, roofs and windows, BMS, LED, educational programmes, window sealing, tap aerators, renewable energy generation	Journal of Cleaner Production
46 [79]	Retrofit of villas on Mediterranean coastlines: Pareto optimization with a view to energy-efficiency and cost-effectiveness	2019	Energy efficiency, pareto model	Building envelope, lighting, renewable energy	Heat pumps, external insulation of walls, window replacement, BMS, LED, PV panels	Applied Energy
47 [80]	Influence of thermal insulation of facades on the performance of retrofitted social housing buildings in Southern European countries	2019	Housing buildings, thermal insulation	Building envelope, lighting, HVAC	HVAC systems, external insulation of walls, LED	Science of the Total Environment
48 [38]	Decision Support System for Sustainable Retrofitting of Existing Commercial Office Buildings	2024	Emission reduction, energy and cost savings, PBP, lower- to medium-rise commercial buildings	HVAC, lighting, equipment improvements	HVAC, lighting, equipment improvements	International Journal of Scientific Research and Management
49 [81]	A systematic review of retrofitting tools for residential buildings	2019	Renovation assessment, financial assessment, transfer of knowledge	Building envelope, lighting, heating/cooling systems improvements	Heat pumps, insulation improvements, LED, BMS	IOP Conference Series: Earth and Environmental Science
50 [82]	Green retrofit of aged residential buildings in Hong Kong: A preliminary study	2018	Green retrofit, energy consumption and gas emission reduction	Building envelope, solar systems, lighting	Insulation of external walls, window replacement with double-glazed, solar systems for water heating/PVs, LED	Building and Environment
51 [83]	An Energy-Resilient Retrofit Methodology to Climate Change for Historic Districts. Application in the Mediterranean Area	2021	Historic regions, climate change	Building envelope, heating/cooling systems improvements	Insulation of walls, roofs, windows, heat pumps, PVs	Sustainability
52 [84]	Climate-Responsive Envelope Retrofit Strategies for Aged Residential Buildings in China Across Five Climate Zones	2025	Energy inefficiency in residential buildings across diverse climates	Building envelope, cooling system improvement	Wall and roof insulation, advanced glazing, airtightness improvements, passive cooling techniques	Buildings
53 [85]	Efficacy of government incentivized residential building retrofits in Canada	2025	High heating/cooling demand in extreme cold and mixed climates	Building envelope, heating/cooling systems improvements	HVAC upgrades, window replacements, thermal insulation, heat recovery ventilation	Nature
54 [31]	A State-of-the-Art Review of Retrofit Interventions in Low-Emission School Buildings Located in Cool Temperate Climates	2025	Overheating in classrooms, poor indoor air quality, high operational costs	HVAC, lighting	Shading devices, smart ventilation, green roofs, lighting upgrades	Buildings
55 [33]	Simulation-Based Multi-Objective Optimization for Building Retrofits in Iran: Addressing Energy Consumption, Emissions, Comfort, and Indoor Air Quality Considering Climate Change	2025	Climate-driven overheating and energy inefficiency in residential complexes	Building envelope, HVAC, Renewable energy	Hybrid HVAC systems, envelope insulation, PV integration	Sustainability
		Non-Specific Climates
		hot-summer–cold-winter
		hot climate (dry/humid)
		cold (and severe) climate
		(mixed) or temperate or mediterranean climate

(Appendix A), which includes the publication year, journal, research problem, renovation activities, and technical approaches proposed.

Table 2. Catalogue of reviewed studies.

ID	Title	Year	Problem	Renovation Activities	Technical Approach	Journal
1 [6]	Study on performance of energy-efficient retrofitting measures on commercial building external walls in cooling-dominant cities	2013	Cooling-dominant cities, energy consumption	Building envelope retrofitting, retrofitting measures on building facades	External and internal insulation, high-reflectivity coating	Applied Energy
2 [12]	Building Energy Retrofit Measures in Hot-Summer-Cold-Winter Climates: A Case Study in Shanghai	2019	Hot-summer–cold-winter climates, energy consumption	Building envelope, equipment system, renewable energy, energy-conserving behaviours, control systems, ventilation	Insulation, cool roofs and coatings, control upgrade, lighting upgrade, thermal storage and heat recovery, solar PV/PVT systems, solar thermal systems, biomass systems, geothermal systems, wind power systems	Energy

Note: ID: a reference number assigned for citation and lookup purposes; Title: full title of the publication; Year: year of publication; Problem: core research problem addressed; Renovation Activities: summary of renovation solutions proposed; Technical Approach: specific methods or strategies for implementation; Journal: name of the publishing journal.

presents a sample of two representative studies to illustrate the cataloguing structure, while the complete dataset of all reviewed publications, including renovation activities and technical approaches, is provided in Appendix A.

3.5. Classification Process

After compiling and recording the selected studies, a classification process was conducted based on two main variables: climate type and building type. The classification results are presented in

Table A2. Proposed interventions per climate type.

Climate	Relevant Articles	Retrofitting
Hot-summer–cold-winter	[2,17,32,36]	Insulation, reflective or cool roofing, control system enhancements, lighting system improvements, thermal energy storage and heat recovery, solar photovoltaic/photovoltaic-thermal systems, solar thermal technologies, biomass energy systems, geothermal solutions, wind energy systems/turbines, double or triple-glazed windows, electrochromic glazing, sun-shading windows, radiative cooling systems, solar chimneys, light-coloured surfaces, green façades, and heat pump technologies.
Hot climate (dry/humid)	[4,5,12,25,28,30,31,38,52]	Insulation, reflective insulating materials, thermal mass components, light-coloured and cool roofing, green façades, solar photovoltaic panels, sensors, mechanical ventilation systems, intelligent building management systems (BMS), lighting improvements, wind energy systems, low-emissivity double-glazing units, electrochromic smart glazing, upgraded window systems, sun-shading windows, radiative cooling solutions, solar chimneys, solar or hybrid air conditioning, and shading elements such as vertical fins, window reveals, overhangs, and shading shelves.
(Severe) cold climate	[3,8,12,18,24,35,51]	Heat pump systems, combined heat and power (CHP) units, thermal insulation of walls and roofs, thermal energy storage solutions, heat recovery ventilation, intelligent control systems, lighting improvements, solar photovoltaic/photovoltaic-thermal installations, solar thermal technologies, and argon-filled glazed window units.
Temperate or mediterranean climate (or mixed)	[16,22,29,39,46,47,49,50]	Thermal insulation, light-coloured and cool roofing, green façades, solar photovoltaic panels, mechanical ventilation systems, sensors, intelligent building management systems (BMS), lighting system upgrades, low-emissivity double-glazed units, sun-shading windows, solar or hybrid air conditioning, and (hybrid) heat pump systems.

and

Table A3. Proposed interventions per building type.

Building Type	Relevant Articles	Retrofitting
Residential	[3,4,7,8,12,15,16,18,19,25,28,30,32,33,36,39,40,41,50,51,53]	Sun-shading elements, gas-filled double- or triple-glazed windows, electrochromic glass, upgraded window systems, radiative cooling technologies, solar chimneys, thermal insulation, air sealing measures, (hybrid) heat pump systems, thermal energy storage units, heat recovery ventilation, building management systems (BMS), green or white roofing, ventilated roof structures, photovoltaic panels, solar or hybrid air conditioning, and LED lighting.
Public/Social	[16,17,20,29,42,43,44,52]	(Hybrid) heat pump systems, thermal insulation, low-emissivity glazed windows, window repositioning and replacement, high-efficiency doors, horizontal and vertical green roofs and walls, inverted roof system components, shading devices, LED lighting, building management systems (BMS), and photovoltaic panels.
Commercial/Office	[1,35,38,45,48]	External and internal insulation for roofs and walls, high-reflectivity surface coatings, argon-filled double or triple glazing for doors and windows, solar thermal systems for heating, photovoltaic panels, LED lighting, HVAC system upgrades, and building management systems (BMS).
Historic/Traditional	[6,21,24,37,46,49]	External and internal insulation of roofs and walls, air sealing measures, low-emissivity double or triple glazing with polyvinyl chloride (PVC) frames, LED lighting, building management systems (BMS), photovoltaic panels, high-efficiency HVAC systems, interior blinds, external overhangs, (water-based) heat pumps, and demand-controlled ventilation (DCV).

Note: For historical and traditional buildings, the applicability of measures such as internal insulation, heat pumps, or façade modifications depends on strict heritage preservation regulations. In many cases, the use of traditional materials and minimally invasive techniques is legally required to maintain architectural authenticity.

(Appendix A), which show the number of studies associated with each category, along with the recommended retrofitting interventions.

Table 3. Recommended interventions by climate type.

Climate	Relevant Articles	Retrofitting
Hot-summer−cold-winter	[2,17,32,36]	Insulation, reflective or cool roofing, control system enhancements, lighting system improvements, thermal energy storage and heat recovery, solar photovoltaic/photovoltaic-thermal systems, solar thermal technologies, biomass energy systems, geothermal solutions, wind energy systems/turbines, double- or triple-glazed windows, electrochromic glazing, sun-shading windows, radiative cooling systems, solar chimneys, light-coloured surfaces, green façades, and heat pump technologies.
Hot climate (dry/humid)	[4,5,12,25,28,30,31,38]	Insulation, reflective insulating materials, thermal mass components, light-coloured and cool roofing, green façades, solar photovoltaic panels, sensors, mechanical ventilation systems, intelligent building management systems (BMS), lighting improvements, wind energy systems, low-emissivity double-glazing units, electrochromic smart glazing, upgraded window systems, sun-shading windows, radiative cooling solutions, solar chimneys, solar or hybrid air conditioning, and shading elements such as vertical fins, window reveals, overhangs, and shading shelves.

Note: Climate: the specific climatic zone addressed in the study; Relevant Articles: publications linked to the given climate; Retrofitting Strategies: energy renovation measures proposed for that climate.

shows indicative examples of retrofit measures across two climate zones. A complete breakdown of all climate-related findings and corresponding retrofit interventions is provided in Appendix A.

Table 4. Recommended interventions by building type.

Building Type	Relevant Articles	Retrofitting
Residential	[3,4,7,8,12,15,16,18,19,25,28,30,32,33,36,39,40,41]	Sun-shading elements, gas-filled double- or triple-glazed windows, electrochromic glass, upgraded window systems, radiative cooling technologies, solar chimneys, thermal insulation, air sealing measures, (hybrid) heat pump systems, thermal energy storage units, heat recovery ventilation, building management systems (BMS), green or white roofing, ventilated roof structures, photovoltaic panels, solar or hybrid air conditioning, and LED lighting.
Public/Social	[16,17,20,29,42,43,44]	(Hybrid) heat pump systems, thermal insulation, low-emissivity glazed windows, window repositioning and replacement, high-efficiency doors, horizontal and vertical green roofs and walls, inverted roof system components, shading devices, LED lighting, building management systems (BMS), and photovoltaic panels.

Note: Building Type: residential, public, commercial, or historical; Relevant Articles: studies that address this building category; Retrofitting Strategies: recommended interventions suitable for the building type.

summarises three representative examples of retrofit strategies by building typology. The full classification, including all reviewed studies, is presented in Appendix A.

4. Analysis

4.1. General Overview

This study is structured around three core analytical axes: climate, building type, and retrofit interventions. While aspects such as cost and payback period are occasionally mentioned, they are not examined in depth within the scope of this work. These variables are highly volatile and country-specific, making their comprehensive analysis challenging in a study dealing with global data. For example, in South Korea, the price of electricity is relatively low, while retrofit costs remain high, resulting in extended payback periods compared to countries where energy prices are significantly higher [45].

Beyond the environmental and direct financial benefits, energy renovation can substantially increase a property’s market value. However, achieving such outcomes requires careful planning and thorough analysis of all key parameters prior to initiating any works. Four main categories of criteria typically guide the selection of suitable renovation strategies:

(a)

Economic parameters, including the cost of each intervention and the estimated payback period.

(b)

Environmental parameters, such as the expected environmental benefits and reductions in greenhouse gas emissions.

(c)

Social parameters, reflecting the improvements in user comfort and the broader societal impact of the intervention.

(d)

Technical parameters, including the feasibility of integrating new systems into the existing infrastructure.

Each of these categories includes multiple influencing factors that shape final decisions. These are inevitably affected by a country’s specific economic conditions, as illustrated earlier. According to [38], key factors include the following:

• Installation cost, which comprises material and equipment costs, labour, and the involvement of qualified professionals in pre-renovation studies, data analysis, and planning. Maintenance and potential future upgrades of installed systems must also be accounted for, as all components have a finite lifespan.
• Payback period, calculated by weighing installation costs against anticipated energy savings, providing an estimate of each intervention’s financial viability.
• Property value increase, which should be considered alongside the energy savings. Renovation can significantly boost a building’s market value compared to its pre-retrofit condition as an energy-inefficient asset.
• Integration feasibility, which involves assessing how well new systems can be incorporated into existing infrastructures during the preliminary design phase.
• Waste management, given that retrofitting projects typically generate waste requiring structured disposal plans.
• Removal of obsolete systems, which may involve bulky and costly equipment. Disposal costs must be anticipated in the initial planning, although incentives or subsidies for recycling may be available in some regions.
• Subsidies and tax incentives, which are often offered by national governments or international programmes to support energy retrofitting efforts.
• Contractor selection, emphasising the importance of choosing reliable professionals who can guarantee the performance of installed systems and materials.
• Performance verification, whereby the achieved post-renovation results should be compared to initial performance projections. Any deviations must be addressed through corrective planning.
• User adaptation, ensuring that building occupants are not adversely affected during or after renovation. New technologies should be intuitive, user-friendly, and easily accepted by the general public.
• Visual and acoustic considerations, particularly the need to minimise noise and visual intrusion during both construction and post-installation operation. For instance, newly installed HVAC systems must be significantly quieter than their predecessors.

When these factors are addressed appropriately and the building’s existing conditions and local climate are assessed from the outset, the benefits of renovation are maximised. The environment benefits from lower greenhouse gas emissions due to reduced reliance on fossil fuels, building users experience improved indoor environmental quality, and owners, shareholders, and tenants benefit from lower energy bills and enhanced property value.

4.2. Review

During the initial phase of the review, it became evident that approximately half of the selected publications focus on residential buildings. This finding is unsurprising, given that the majority of the global building stock comprises residential units. Every household requires a living space, and residential dwellings typically accommodate fewer occupants than commercial or public buildings—commonly housing just four to five individuals. Consequently, a greater number of residential buildings is needed to satisfy housing demand, explaining their prevalence in retrofitting literature.

As illustrated in Figure 5, residential buildings account for 51% of the reviewed studies. The remaining publications are almost evenly distributed across other building types, with the lowest representation (14%) corresponding to commercial or office buildings.

Regarding climate representation, the reviewed literature demonstrates a relatively balanced distribution across the major climate zones as depicted in Figure 6. Cold, hot, and temperate/mixed climates each account for between 25% and 29% of the studies. In contrast, climates characterised by hot summers and cold winters are addressed in only 17% of the publications—understandably so, given that these conditions are geographically limited to specific regions, such as parts of China.

The review identified the following major categories of retrofit interventions reported across the selected studies:

• Thermal insulation.
• Heat pumps/upgrades to heating, cooling, and ventilation systems.
• Lighting upgrades.
• Photovoltaic (PV) systems.
• Biomass, geothermal, and wind energy systems.
• Window upgrades.
• Smart sensors and building management systems.
• Mechanical ventilation.
• Heat recovery ventilation systems.
• Cool, white, and green roofs.
• Hybrid HVAC systems.
• Shading devices.
• Solar chimneys and ventilation stacks.

These interventions reflect a diverse set of strategies that have been implemented globally to enhance the energy efficiency and environmental performance of buildings across different climates and building typologies.

4.3. Interventions by Climate Type

Figure 7 presents the frequency with which each retrofit intervention appears across the four climate categories. A value of 25% indicates that an intervention is applicable to only one climate type, while 100% signifies suitability across all four types. For instance, insulation is applicable in all climates—with appropriate adaptations—since it provides thermal protection against both high and low temperatures. Other universally applicable measures include intelligent sensors that dynamically adjust heating and cooling systems, photovoltaic (PV) systems, and high-performance glazing, all of which contribute to reducing thermal losses during both cold and hot seasons. In addition, lighting upgrades—such as replacing conventional bulbs with LED technology—are recommended for all climates, offering a highly cost-effective means of significantly reducing electricity consumption.

Conversely, some measures are more climate-specific. For example, heat recovery ventilation is predominantly recommended for cold and very cold climates, where year-round heating is often necessary.

Further insights can be derived when combining the information with Table A2 (Appendix A):

• Heat pumps appear in 75% of cases, being appropriate for temperate and (very) cold climates, as well as areas with cold winters. These systems are prevalent in such regions due to the extended heating demand and their relatively low installation and maintenance costs.
• Cool roofs and sun-shading devices are also applicable in 75% of the cases, primarily in hot and temperate climates or regions with warm summers. Their popularity is driven by their capacity to reduce solar gains, their affordability, and short payback periods.
• More alternative energy systems—biomass, geothermal, and wind—have been cited in studies dealing with climates characterised by hot summers and cold winters, or in cold regions, accounting for 50% of cases. These are typically considered in areas lacking abundant solar radiation as alternatives to PV systems.
• Mechanical ventilation and solar/hybrid air-conditioning systems are found to be more suitable for hot and mixed climates, where cooling is required for extended periods, and solar availability supports the operation of such systems.
• Solar chimneys—less frequently cited—are proposed for hot climates or those with humid summers, as they enhance natural ventilation. Their limited use may be attributed to the specificity of their climatic suitability and the scale of renovation required compared to other simpler technologies, such as hybrid air-conditioners.

Figure 8 provides a Venn diagram that visually summarises these climate-intervention overlaps.

Moreover, both Figure 8 and Table A2 suggest that in hot and temperate climates—where cooling is essential—there is a broader array of interventions for improving efficiency and cost-effectiveness. This is largely due to the favourable solar conditions, which enhance renewable energy generation potential.

The frequency of intervention use depends on several factors, including technical effectiveness, installation and maintenance complexity, and associated costs and payback time. Among the most commonly adopted and effective strategies is thermal insulation, which can be installed internally or externally, including on roofs. Its long-standing use, minimal disruption during installation, and applicability across climates make it attractive. The key advantage of insulation lies in its adaptability to different climatic contexts, offering benefits not only for energy efficiency but also for enhancing the building envelope.

Adaptations include the following:

• In cold climates, insulation is best applied externally.
• In hot climates, external insulation should include reflective materials to repel solar radiation.
• In roof insulation, materials like polyisocyanurate are preferred in hot climates, while polystyrene is commonly used for wall insulation.
• Phase change materials (PCMs) are recommended across all climates, tailored to regional needs.
• In areas with low diurnal temperature variation, internal insulation is preferred, whereas external insulation is more suitable where such variations are greater.
• Furthermore, thermal bridging can be mitigated using specialised sealing tapes around vulnerable areas, such as window frames.

Similarly, advanced glazing systems have gained popularity. Double and triple glazing with low-emissivity coatings significantly reduce heat losses in winter and heat gains in summer. New technologies—like gas-filled low-e double-glazed units—are effective in warm climates, with moderate payback periods and affordable costs. Triple glazing offers even greater efficiency, albeit at a higher initial cost. Reflective coatings are also applied in high solar radiation regions. Electrochromic glazing has shown promising results, reducing heat gains by up to 50% [42].

Another passive strategy more suitable for new constructions than retrofits is strategic window sizing and orientation. According to [45], minimising south-facing window area and maximising north-facing glazing can lower cooling loads while enhancing daylight availability.

In terms of HVAC systems, solar-powered or hybrid cooling systems provide cost-free operation, leveraging solar resources. Intelligent sensors, often integrated with thermostats, activate heating/cooling systems based on environmental conditions, ensuring thermal comfort and hot water availability without user input. Other sensor technologies, such as motion detectors for lighting, contribute to energy savings and are increasingly embedded in various household appliances and systems.

Among the most widespread and cost-effective interventions are LED lighting upgrades. Although not directly influencing heating or cooling demand, they substantially reduce electricity consumption. With a short payback period ranging from a few months to two years [3], they can be further enhanced by optimising lighting power density.

Smart sensors, which adjust energy systems based on real-time data, also show significant potential. They are relatively inexpensive and easy to install, especially in thermostats, sockets, and lighting systems. As integration increases, these systems are expected to play a central role in next-generation building management.

PV systems remain among the most versatile solutions, applicable across climates. However, their performance is inherently tied to solar availability. Their uptake has grown thanks to policy incentives and subsidies, enabling citizens to produce clean energy independently. Similarly, solar chimneys are well-suited to sunny regions needing improved ventilation due to high humidity.

Roof insulation is often treated as a distinct category. Cool roofs and green roofs are the two main strategies, and are especially relevant in hot, temperate, and warm-summer climates. Cool roofs, with high reflectivity, can be up to 33 °C cooler than traditional roofs, leading to interior temperature reductions of around 20 °C and cooling energy savings of up to 20%.

Meanwhile, green roofs absorb up to 30% of solar radiation and mitigate stormwater runoff—up to 50% of rainwater is returned to the natural cycle. They also offer acoustic and particulate filtration benefits. However, they come with higher costs, maintenance requirements, and spatial demands.

Heat pumps are considered an emerging intervention category. Easy to install and relatively compact, they offer promising decarbonisation potential in temperate and cold regions. A recent study found that replacing gas boilers with high-efficiency heat pumps could reduce primary energy use by 60% and CO₂ emissions by 90% across the EU by 2050, while halving natural gas imports and contributing 3.5% to emission reduction targets [7].

Shading systems—both passive (e.g., awnings) and dynamic (e.g., electrochromic glazing)—also play a role in reducing solar gains and enhancing indoor comfort.

Despite their high efficiency, some renewable technologies, such as wind turbines, are less popular due to visual and acoustic concerns, particularly in residential areas. Wind systems require substantial space and can generate noise pollution, discouraging widespread adoption [46].

Ultimately, optimal performance stems from context-specific combinations of interventions tailored to both climate and user needs.

4.4. Interventions by Building Type

As previously highlighted, before implementing any intervention, a thorough analysis of the building’s energy requirements, which also depend on its usage, is essential. This process involves documenting existing energy systems, measuring energy consumption, and assessing potential energy savings. Technical interventions are selected according to the building type to effectively address specific requirements. Additionally, the needs of users, such as residents, office employees, or individuals in hospitals, schools, etc., are also considered. New technologies should be user-friendly and should not negatively impact users’ daily routines.

4.4.1. Residential Buildings

According to Table A3 (Appendix A), most interventions can be applied to residential buildings, which constitute the majority of buildings. This assumes they are not housed within listed or specially regulated buildings.

One fundamental intervention, easily applicable in any home regardless of climatic conditions, is thermal insulation. Thermal insulation is considered essential for residential buildings as it significantly reduces thermal losses, saving electricity used for heating and cooling. Consequently, it improves occupants’ thermal comfort, which is a critical feature, as people desire adequate heating and cooling to maintain comfort in their homes. Replacing old windows with energy-efficient double or triple low-emissivity glazing, incorporating special coatings, substantially enhances the effectiveness of insulation by reducing thermal losses. Window frames, often wooden and susceptible to air infiltration, also play a significant role. For optimal outcomes, frame replacement is recommended alongside glazing replacement. Alternatively, insulating materials and specialised sealing tapes can be installed on vulnerable areas.

In cold climates and regions with severe winters, enhancing the efficiency of heating systems is crucial. Installing heat pumps, which are considerably more efficient than traditional central heating systems and conventional air conditioning units, is recommended to reduce electricity consumption for heating homes. Additionally, replacing basic ventilation systems with mechanical ventilation systems equipped with heat recovery can limit energy losses. Conversely, in warm or temperate climates with hot summers, where efficient cooling is required for most of the year, conventional air conditioners can be replaced with hybrid or solar-powered systems. Adequate mechanical or natural ventilation is also essential to reduce cooling loads. Cost-effective shading devices are easy to install, blocking solar radiation from entering buildings and reducing cooling demands.

Due to the energy crisis, prudent use of air conditioning is widely adopted. Occupants of energy-inefficient buildings, unable to invest in new technologies, can reduce electricity consumption by limiting the use or intensity of air conditioning. Studies indicate that reducing conventional air conditioner intensity by one degree can yield 1–8% energy savings, translating into immediate economic benefits. A more substantial energy saving of approximately 20% can be achieved by avoiding air conditioning usage at night, provided there is sufficient room ventilation [43].

The most impactful intervention is renewable energy generation, such as solar, wind, and geothermal energy. Photovoltaic (PV) systems are most widespread, being familiar to the general public, flexible in placement, state-subsidised, and highly efficient, especially in sunny regions. PV systems can be installed on roofs, building facades, and surrounding areas, providing flexibility in finding suitable installation spaces. Wind turbines and geothermal systems require more available space and higher initial investment. Geothermal energy is increasingly utilised in residences through water-to-ground heat pumps, also supported by subsidies.

4.4.2. Historic and Traditional Buildings

Unlike residential buildings, historic buildings require more delicate handling during renovations, restricting available intervention options. Due to their historical significance, reconstruction is either not recommended or outright prohibited. Given their age, historic buildings are considerably less energy-efficient, thus even minor interventions can potentially reduce energy consumption by up to 60% [44].

Simple interventions that can be applied without compromising buildings’ character include upgrading heating, cooling, and ventilation systems to modern, more efficient, and environmentally friendly alternatives. Existing systems account for most of the energy consumption within these buildings, often failing to deliver adequate comfort in all spaces. Ventilation significantly influences indoor air quality and occupant comfort, thus ventilation system upgrades should be prioritised, as they do not affect the historic value and incur relatively low costs.

Additionally, thermal insulation can be installed internally on walls and roofs. In certain cases, external insulation may be recommended provided it does not alter the building’s façade. Upgrading lighting systems to energy-efficient LED bulbs is equally important, significantly enhancing illumination and user-friendliness. Upgrading to LED lighting represents a straightforward, cost-effective approach to reducing energy consumption and should be considered among the first steps taken by building managers.

Since many historic buildings are not occupied daily and occupancy fluctuates, installing smart sensor systems to regulate temperature, lighting, and other parameters based on actual usage is beneficial. In large buildings, these sensors can integrate into a comprehensive building management system capable of monitoring and recording air and water flow rates, humidity levels, and temperature fluctuations. Utilising this data, the system can adjust heating, cooling, and ventilation settings according to occupancy levels, creating optimal indoor conditions while maximising energy savings.

Interventions altering wall-to-window ratios or moving window openings are not permitted in historic buildings. However, interior blinds or shading devices can easily be installed, allowing regulation of solar radiation and reducing cooling demands during summer. Exterior shading structures can also be added in certain cases. Another effective intervention is replacing existing windows with energy-efficient double or triple low-emissivity glazing, along with suitable frames and airtight sealing tapes, wherever feasible and consistent with a building’s historic structure.

Where more robust energy interventions are possible, selecting an appropriate renewable energy system is vital. Photovoltaic (PV) systems, widely recognised and frequently installed on building roofs, are the most common choice. Recent technological advances enable the integration of PV systems on traditional tiled roofs. Nevertheless, installing PV systems on particularly old buildings may sometimes be unfeasible. Detailed structural evaluations must precede installation to ascertain the building’s capacity to support and maintain these systems. Additionally, a cost–benefit analysis should be performed, as historic buildings often lack sufficient roof space for full-scale PV installations, rendering such interventions economically unattractive. Furthermore, appropriate permissions must be secured from relevant authorities, as these buildings frequently fall under governmental or institutional oversight, requiring approvals from entities like archaeological services. Specific structures, such as churches, categorically prohibit such interventions.

Therefore, where adequate space exists, PV installations can be situated in adjacent areas, such as courtyards, without physically attaching them to the building. This strategy avoids potential damage, preserves historical value, and simplifies approval processes [47]. The same approach may be applied to non-historic older buildings at risk of roof damage or with insufficient roof space for PV installations.

4.4.3. Commercial and Office Buildings

In large-scale buildings, such as commercial buildings and office facilities accommodating numerous employees, centralised systems typically handle heating, cooling, and ventilation. This practice also applies to public or social buildings and historic buildings converted into educational institutions or with similar uses. Contrary to typical practices in our country—such as radiators for heating, air conditioners or fans for cooling, and windows for ventilation—in some countries, HVAC (Heating, Ventilation, and Air Conditioning) systems are standard in residential buildings as well. Most of these systems are either as old as the buildings or were installed before the recent energy crisis, making them obsolete by contemporary energy-efficiency standards. According to literature [3], outdated HVAC systems account for over 40% of energy consumption in buildings, particularly in regions with hot climates and high humidity [6]. Although upgrading HVAC systems entails higher costs and longer payback periods than other measures, it yields the highest energy savings and substantially reduces greenhouse gas emissions. Therefore, upgrading these systems is essential for all building types, potentially lowering electricity consumption by up to 30% [5,47].

In non-residential buildings, HVAC systems typically operate continuously throughout the day, even without occupancy. Thus, upgraded systems should include control mechanisms or smart sensor technologies, activating the systems shortly before working hours to achieve desired temperatures promptly, and automatically deactivating during periods of inactivity. Such zero-cost interventions can save approximately 25% in electricity consumption [3]. Similar strategies can be adopted in residential buildings by programming system usage only during necessary hours.

In office, service, and commercial buildings, thermostat adjustments—raising summer temperatures by one degree and lowering winter temperatures by one degree—can further reduce energy consumption without compromising user comfort.

According to the same reference, the second most significant upgrade factor for reducing electricity consumption in large commercial buildings is lighting. Analytical models indicate fluorescent lamps constitute about 20% of total energy consumption in these buildings. Replacing these with LED lamps reduces energy consumption by approximately 7% [3]. This intervention is cost-effective, with estimated payback periods under two years.

Another essential retrofit in commercial buildings involves window upgrades, as windows significantly contribute to thermal losses, especially in regions experiencing extreme heat or cold. Replacing conventional windows with double or triple low-emissivity glazing, possibly incorporating reflective coatings, can reduce thermal losses and electricity consumption by up to 15% in some buildings [3]. Window replacements typically accompany thermal insulation improvements in walls and roofs, optimising thermal load reductions. Payback periods depend on building-specific needs, selected window and insulation materials, and economic conditions within each country.

Another significant intervention in large-scale buildings is installing PV systems to generate onsite electricity, enhancing independence from national grids. These buildings usually possess sufficient roof space to accommodate ample PV installations. Despite requiring significant upfront investment and longer payback periods (unless subsidised), this measure greatly reduces electricity bills—often to near-zero levels—while generating clean energy and contributing significantly to environmental protection.

Alternatively, available roof space in commercial buildings may be converted into green roofs, providing thermal insulation and recreational areas for employees and customers. Proper management can even generate additional revenue from external visitors.

However, commercial building stakeholders often prefer interventions yielding short payback periods and immediate results, such as lighting, insulation, and HVAC system upgrades. Combined implementation of these measures, alongside partial PV installations, can achieve electricity consumption reductions of up to 30%, reduce pollutant emissions by 25%, improve thermal comfort, and enhance indoor air quality [5,47].

4.4.4. Public and Social Buildings

Public buildings serve diverse purposes, thus their energy needs vary significantly depending on their functions. Electricity consumption is distributed differently across building types, as illustrated in

Table 5. Distribution of energy consumption by building use (* includes energy consumed for pool water heating).

Energy Use	Schools	Fitness Centres	Hospitals	Government Offices	Swimming Pools
Heating/Cooling	40–50%	45–55%	35–45%	30–40%	55–65% *
Lighting	20–30%	15–25%	20–30%	25–35%	10–20%
Water Heating	8–12%	8–12%	8–12%	8–12%	8–12%
Equipment	4–6%	4–6%	8–12%	8–12%	4–6%
Ventilation	4–6%	4–6%	4–6%	4–6%	2–4%

, compiled from official European sources [5].

As shown in Table 5, heating and cooling constitute the largest share of energy consumption across all building types, followed by lighting. These categories should thus be prioritised for upgrades to achieve substantial energy consumption reductions. Swimming pools have notably high heating demands, as significant energy is required to maintain water temperatures year-round, even under extremely cold outdoor conditions. Schools and fitness centres should primarily focus on upgrading heating and cooling systems, while offices should additionally prioritise lighting improvements. Replacing old fluorescent bulbs with LEDs is recommended across all building types, as LEDs are significantly more energy-efficient and provide superior lighting conditions.

Specifically, in hospitals, upgrading heating, cooling, and ventilation systems is essential for operational efficiency and patient comfort. Modern HVAC systems reduce overall energy consumption, while energy management systems optimise consumption monitoring and system operation. Thermal insulation in walls and roofs and replacing old windows with double or triple glazing further minimise thermal losses and enhance thermal comfort. These measures, combined with LED lighting upgrades, substantially improve energy efficiency and indoor environmental quality, which are vital in healthcare facilities.

In schools, upgrading the building envelope through enhanced wall and roof insulation and window replacements significantly reduces thermal losses and energy use. HVAC systems must also be modernised to ensure comfortable indoor conditions for students and staff. Given that schools remain unoccupied for extended periods, implementing automated management systems to deactivate HVAC systems outside school hours and during holidays is crucial. Additionally, installing photovoltaic systems on walls, roofs, or school grounds can reduce energy consumption by up to 30% and emissions by 25% [5]. Excess energy generated during the summer, when schools are closed, can be redistributed to nearby residences and businesses. Educational institutions also present ideal environments to raise awareness and promote energy conservation through educational activities.

Specialised facilities like swimming pools require targeted solutions, such as replacing traditional water heating systems with solar heaters or heat pumps, enhancing energy efficiency. Heat recycling from water to heat adjacent spaces further optimises energy usage. These measures, along with LED lighting, significantly improve users’ thermal comfort and reduce environmental impacts.

In museums, upgrading air conditioning and lighting systems is vital for saving energy and protecting exhibits, which require precise temperature, humidity, and lighting conditions. LED lighting reduces heat and UV emissions, offering a straightforward and effective approach to lowering energy costs. Energy management systems maintain optimal indoor humidity and temperature levels regardless of external weather conditions, protecting exhibits and enhancing visitor comfort. Smart sensor-controlled internal or external shading devices can further protect against solar radiation, adjusting coverage based on the sun’s position and intensity.

These interventions support the development of sustainable, energy-efficient public buildings suitable for all climate zones while promoting environmental awareness and resource conservation.

5. Discussion and Conclusions

A significant portion of the global building stock is over 50 years old and therefore not energy-efficient, accounting for approximately 40% of the total energy consumed worldwide [39]. Simultaneously, climate change is a pressing concern for governments across the globe, as temperatures continue to rise at an alarming rate. Consequently, the building sector has become central in discussions about energy upgrades, offering substantial potential for reducing both energy consumption and greenhouse gas emissions through targeted retrofitting measures.

The process of selecting appropriate interventions for the energy renovation of buildings is complex, as it involves multiple factors that must be considered to develop a comprehensive plan. Among the most critical factors influencing the decision-making process are the climate of the region, the building type, and the economic context of each country. In this study, the first two factors are analysed in detail. The findings are based on data gathered from case studies of individual buildings, aiming to provide practical guidance on suitable interventions across different climatic conditions and building types.

The general conclusions drawn with respect to building typologies are as follows:

• The vast majority of buildings are residential in nature, and a wide range of retrofit measures can be applied to this category.
• Historic buildings present the most restrictions, as they are subject to heritage conservation regulations. Any intervention must be approved by the relevant authorities to ensure that the building’s historical value is preserved.
• In the case of public buildings, the choice of interventions should take into account the intended use of the facility—whether for education, sports, or other public services—often requiring specialised retrofitting strategies [5].
• For commercial buildings, stakeholders usually lead the decision-making process and tend to prioritise interventions with low upfront costs and short-term returns [47].

The analysis of the reviewed studies reveals several key patterns and limitations that shape the current state of climate-sensitive retrofit strategies. A clear climate-driven trend emerges, with warm and hot-summer regions prioritising reflective insulation, ventilated façades, cool or green roofs, and shading systems, while cold climates focus predominantly on thermal envelope upgrades, high-performance glazing, and advanced HVAC or heat pump technologies. Temperate and Mediterranean regions generally adopt hybrid solutions that combine insulation with passive cooling interventions, enabling more balanced performance improvements. Despite this observed alignment between retrofit strategies and climatic conditions, the literature lacks a standardised methodological framework for evaluating cost-effectiveness, scalability, and replicability across diverse contexts. Moreover, while several studies highlight the potential of advanced technologies—such as photovoltaic systems, electrochromic glazing, and geothermal energy—their widespread adoption remains limited. High upfront costs, aesthetic restrictions in heritage buildings, and space constraints in dense urban environments often prevent these theoretically effective solutions from achieving their full practical potential.

Beyond the climate-driven insights, the findings expose significant gaps in the coverage, integration, and validation of retrofit measures, as summarised in

Table 6. Synthesis of critical observations derived from the reviewed studies, highlighting patterns, biases, and research gaps across climate zones and building types.

Observation	What We Found	Critical Insight
Climate-driven strategies	Different priorities between hot, cold, and temperate zones	No unified evaluation framework
Effectiveness vs. feasibility	High-tech solutions suggested but rarely implemented	Practical constraints are underexplored
Coverage bias	75% warm climates + residential focus	Cold zones + heritage/commercial underrepresented
Lack of integration	Measures analysed individually	Misses synergies, cost–performance trade-offs
Validation gap	Heavy reliance on simulations	Empirical, real-world studies are scarce

. Approximately 75% of the reviewed studies focus on warm or temperate climates, leaving cold and mixed climatic regions underrepresented. Similarly, residential buildings dominate the literature, whereas heritage, commercial, and public buildings—often facing unique technical and regulatory challenges—remain insufficiently addressed. Furthermore, most studies evaluate interventions in isolation rather than considering multi-objective optimisation or potential synergies between combined measures, such as integrating shading systems, insulation, and renewable energy production. This narrow analytical approach limits the ability to identify solutions that balance energy efficiency, comfort, lifecycle costs, and carbon emissions. Finally, the review highlights a persistent performance gap: the majority of studies rely on simulation-based assessments without validating predictions against real-world, post-renovation data. This lack of empirical evidence restricts the robustness and generalisability of findings, underscoring the need for research that integrates monitoring with modelling to bridge the gap between theoretical potential and practical outcomes.

While technical solutions dominate much of the literature, the reviewed studies also reveal that policy frameworks and financial mechanisms play a decisive role in shaping retrofit adoption rates. For example, interventions such as heat pump installations and photovoltaic systems are more commonly implemented in countries offering subsidies or tax incentives, whereas high-capital solutions like green roofs remain less prevalent due to limited financial support. The variability of policy-driven funding across regions partially explains why similar technical solutions achieve different levels of penetration. This underscores the importance of integrating policy and economic considerations into future analyses of retrofit strategies.

The findings also reveal that the successful adoption of energy retrofit measures depends strongly on the interplay between technical potential and financial feasibility. In several cases, technically effective solutions, such as photovoltaic systems, electrochromic glazing, and heat pumps, achieved high penetration rates only in regions offering subsidies, tax incentives, or low-interest financing schemes. Conversely, interventions like green roofs and geothermal systems remain underutilised, despite demonstrated energy benefits, due to limited policy support and high upfront investment costs. This divergence underscores the importance of coupling retrofit strategies with robust policy frameworks and accessible financing mechanisms to ensure large-scale implementation and equitable adoption across different socio-economic contexts.

5.1. Proposed Interventions and Results

From the above analysis, several key findings emerge regarding recommended interventions by climate zone and building type:

• Thermal insulation is among the most widely adopted measures for reducing heat losses. It is applicable across all climatic conditions and can be installed either internally or externally on walls and roofs, depending on the needs of the building. Multiple studies confirm its effectiveness, with reported energy savings ranging from 25% to 50% depending on the insulation strategy [6,40,48]. In warm climates, the use of reflective insulation materials can result in energy savings of up to 25% [46]. In such cases, insulation should ideally be applied on the external surfaces of exterior walls.
• In warm climates, insulation of the roof in the form of cool or green roofs is also recommended. These systems reflect or absorb solar radiation, respectively, thereby reducing cooling energy demand by 20–30%. However, several studies note that green roofs require higher upfront investment and more demanding maintenance compared to cool roofs, which explains their lower adoption despite their long-term benefits [41,46].
• Window retrofits are considered one of the most effective interventions across all climate zones and building types. Replacing old windows with low-emissivity (low-e) glazing can reduce heat losses by up to 65% [19]. In warm climates, glazing should include reflective coatings to deflect solar radiation. Alternatively, electrochromic windows, which adjust their transparency based on the intensity and angle of incoming light, can reduce indoor heat gains by as much as 50% [42].
• Studies indicate that, in hot climates, minimising south-facing window openings while maximising those facing north can reduce cooling loads and simultaneously improve daylight penetration [45]. However, this intervention remains rarely implemented because it requires extensive architectural modifications and can compromise façade aesthetics [49].
• The role of HVAC systems is crucial, particularly in large buildings with multiple users, residents, or visitors. These systems can account for up to 70% of total building energy consumption and replacing them with high-efficiency alternatives can reduce electricity bills by up to 35% [3,6].
• When combined with building management systems (BMS) that regulate operating schedules, indoor temperature, and humidity levels, energy savings can increase by a further 25%, with virtually no operational cost [50]. As a result, BMS are deemed essential for all building types and climate zones.
• Fluorescent lighting contributes to approximately 20% of energy consumption in large commercial, institutional, or office buildings [3]. Replacing these with LED lamps can lead to substantial reductions in energy demand, as LEDs consume up to 80% less energy. Given their low replacement cost, short payback period, longer lifespan, and improved lighting conditions, LED upgrades are easily applicable across all building types and climates. Moreover, they can be integrated into the building’s central management system.
• Perhaps the most impactful intervention in terms of reducing electricity bills and improving a building’s carbon footprint is the installation of photovoltaic (PV) systems, enabling the production of clean energy and reducing dependence on the grid. Their effectiveness depends on adequate available space and high annual solar exposure. Due to their flexible installation options, PV systems can even be deployed in outdoor spaces adjacent to heritage buildings without affecting their aesthetic or historical value. Although PV systems require higher initial investment, numerous governmental support schemes are available to accelerate payback and promote adoption.
• Other renewable energy technologies, such as wind or geothermal systems, can also be considered for on-site energy generation. However, their implementation in dense urban areas is less feasible due to spatial constraints, higher capital costs, and the potential for disturbances to residents [12].
• Heat pumps are increasingly being supported by subsidy schemes and are particularly suitable in areas where efficient heating is essential. Their installation is typically straightforward and cost-effective, and they offer superior energy performance compared to traditional air conditioners and central heating systems.
• It is therefore reasonable to conclude that a combination of carefully selected retrofit measures tailored to the specific characteristics of a building and its climatic context yields optimal results-achieving up to 70−80% energy savings.
• Finally, the analysis reveals that warm climates offer more opportunities for efficient and cost-effective cooling interventions. This aligns with the fact that warm, temperate, and hot-summer climates represent 75% of the studies reviewed.

Table 7. Optimal retrofit interventions per climate type.

Climate	Optimal Retrofit Interventions	Building Type	Comments
Warm, temperate, and hot-summer climates	Reflective insulation on external walls and roofs	All building types	Subject to conditions in historic buildings—25−50% energy savings
	Photovoltaic systems	All building types	Subject to conditions in historic and commercial buildings
	Solar/hybrid air conditioning, upgraded cooling and ventilation systems	All building types
	Reflective coatings on double/triple glazing, electrochromic windows	All building types	Subject to conditions in historic buildings—up to 50% reduction in incoming solar heat
Cold climates and climates with harsh winters	Internal wall insulation	All building types
	Heat pumps, upgraded heating systems	All building types
	Replacement of windows and frames	All building types	Subject to conditions in historic buildings—60% reduction in thermal losses
All climates	Replacement of lamps with LED lighting	All building types	80% lower energy demand
	Building Management Systems (BMS)	All building types	25% energy savings

Note: For historical and traditional buildings, the applicability of certain retrofit measures (e.g., internal insulation, heat pumps, façade alterations) may be constrained by strict heritage preservation regulations. In many cases, the use of traditional materials and minimally invasive techniques is legally required to maintain architectural authenticity.

summarises the conclusions regarding optimal retrofit interventions per climate and building type as presented in the current sub-section.

5.2. Limitations and Future Research Directions

In conclusion, the literature review revealed that the majority of the studies focused on residential buildings, which is expected given that they constitute the bulk of the global building stock. At the same time, there is a noticeable lack of studies pertaining to regions such as the United States and Australia. Similarly, limited data are available for Saudi Arabia and its neighbouring countries. Future research could focus on collecting relevant data and proposing suitable retrofit interventions for these underrepresented areas.

Beyond the evident lack of geographic representation, and despite the abundance of studies on Europe and Asia, most of the reviewed publications rely on simulations and theoretical modelling of energy interventions. This highlights a significant gap in the availability of empirical data and validated performance outcomes of the proposed retrofit measures in real-world applications [3]. A critical limitation of these studies is the absence of an applied methodology that compares the expected (modelled) results with actual post-renovation outcomes [8]. This gap may lead to confusion among stakeholders and significantly restricts the practical relevance of this review, as the findings are not based on implemented projects. Future work could address this shortcoming by focusing on building retrofits supported by verified, real-life performance data.

Although quantitative performance data were reported where available, a unified meta-analysis was not feasible due to significant variations in study methodologies, baseline assumptions, and reported performance metrics. This heterogeneity prevents direct comparison of energy savings across interventions and contexts. Future studies should aim for more standardised reporting of energy savings to enable comparative assessments across climatic contexts and retrofit strategies.

Furthermore, most studies lack a holistic proposal that could, with appropriate adaptations, be scaled to meet the retrofit needs of a large number of buildings. Instead, the majority are limited to case—specific scenarios using simulation models. This study aimed to address that research gap by adopting a broader analytical approach that does not focus on a single region or building. It presents comprehensive retrofit proposals based on two key parameters: climatic conditions and building type. As a result, any tenant, owner, stakeholder, or building manager seeking to undertake renovation works can consult this study to identify recommended interventions tailored to the specific building function and the climatic context of the area.

Moreover, this review primarily focused on identifying retrofit strategies and their technical performance across climatic and building contexts. While financial aspects, such as subsidies or high upfront costs, were occasionally discussed, a systematic comparative analysis of economic performance and life-cycle costs was beyond the scope of this study due to inconsistent cost data across the reviewed literature. Future research should integrate comprehensive financial evaluations, including cost–benefit analyses, lifecycle costs, and payback periods, to better inform policy, investment decisions, and the feasibility of retrofit interventions relative to a building’s remaining service life.

Considering that a lack of initial capital and the high cost of full-scale renovations often act as barriers to retrofitting, it is essential to conduct a techno-economic assessment in the second phase of decision-making to evaluate the feasibility of the selected interventions. Factors such as cost and payback period play a crucial role in final decision-making [51]. Although this study did not delve into economic analysis, it paves the way for future research in that direction. A comprehensive global economic assessment remains challenging, as costs and payback periods vary significantly depending on each country’s economic conditions. However, indicative analyses could be conducted for European countries—where the strictest energy and emissions regulations have been adopted—and for countries like China, where there is a rich body of literature on energy-related topics.

Additional proposals for expanding current studies include the following:

• Renovation processes may result in construction waste and additional emissions. Therefore, future studies should examine this environmental parameter [51].
• Future research should also focus on community-scale analyses rather than individual buildings, aiming to improve energy performance at a district or neighbourhood level.
• The next generation of decision support systems should enable interactive use of methodologies that incorporate data from implemented projects and provide recommendations in real time. When coupled with findings from inclusive studies, such systems can significantly enhance the decision-making process [5].

Finally, it is evident that global energy demand continues to grow, making it increasingly difficult to meet long-term targets set for 2050. For this reason, research into building energy efficiency must remain dynamic and continuously offer new solutions and interventions for greater energy savings.